Propylene random copolymers and processes for preparing same

ABSTRACT

A random copolymer of propylene with from 1 to 10 mol % of a C 4  to C 20  α-olefin and an intrinsic viscosity of 0.5 to 6 dl/g is also characterized by a melting point (Tm) measured by a differential scanning calorimeter falling within the range of 90&lt;Tm&lt;155-3.5(100-P) (wherein P is the propylene content (mol %) present in the copolymer), a molecular weight distribution (Mw/Mn) of less than 3.5, and a boiling trichloroethylene-insoluble content of less than 5% by weight. Terpolymers of propylene-ethylene-C 4  -C 20  α-olefin wherein Tm falls within the range of 70&lt;Tm&lt;155 -5.5(100-P) are also described. The propylene random copolymer is prepared by polymerizing propylene, α-olefin, and optionally, ethylene in the presence of a catalyst system which includes an hafnium compound having a multidentate ligand and two or more cycloalkadienyl groups linked together via an alkylene linkage, and an organoaluminum oxy-compound.

This is a division of application Ser. No. 07/459,834 filed Jan. 31,1990, now abandoned.

FIELD OF THE INVENTION

This invention relates to novel ethylene copolymers and a process forpreparing the same and more particularly to novel ethylene copolymersexcellent in flowability in spite of the fact that they are narrow inmolecular weight distribution (Mw/Mm) in comparison with conventionallyknown ethylene copolymers, and to a process for preparing the same.

In a further aspect, the invention relates to novel propylene randomcopolymers and a process for preparing the same and more particularly tonovel propylene random copolymers ]laving low melting points incomparison with conventionally known propylene random copolymers and, inparticular, excellent in heat-seali.g properties and anti-blockproperties, and to a process for preparing the same.

In another aspect, the invention, relates to olefin polymerizationcatalysts capable of polymerizing olefins with excellent polymerizationactivity even when the amount of aluminoxane used is reduced and capableof giving olefin polymers having high molecular weights.

BACKGROUND OF THE INVENTION

When molded into articles such as film, copolymers of ethylene andα-olefins of 3 to 20 carbon atoms are found to have excellent mechanicalstrength such as tensile strength, tear strength or impact strength andalso excellent heat resistance, stress crack resistance, opticalcharacteristics and heat-sealing properties in comparison withconventional high-pressure low density polyethylenes, and are known asmaterials particularly useful for tile preparation of inflation film orthe like.

Generally speaking, the ethylene copolymers mentioned above have suchexcellent characteristics that when said copolymers come to be narrowerin molecular weight distribution represented by the ratio (Mw/Mn) ofweight average molecular weight (Mw) to number average molecular weight(Mn), the molded articles obtained therefrom, such as film, are found tobe less tacky. However, widen these ethylene copolymers having a narrowmolecular weight distribution are melted, there were such drawbacks thattheir flowability represented by the ratio (MFR₁₀ /MFR₂) of MFR₁₀ undera load of 10 kg to MFR₂ under a load of 2.16 kg as measured at 190° C.is small, with the result that they become poor in moldability.

Therefore, if ethylene copolymers which are small in value of Mw/Mn andnarrow in molecular weight distribution and, moreover, large in value ofMFR₁₀ /MFR₂ and excellent in flowability come to be obtained, suchethylene copolymers are certainly of great commercial value.

On the other hand, polypropylene has wide applications in the field ofplastics because of its excellent physical properties. For example,polypropylene is widely used as packaging film material. In theapplications of the type, however, because of its relatively highmelting point, polypropylene is generally copolymerized with ethylene orα-olefins of 4 to 20 carbon atoms in order to improve heat-sealingproperties at low temperature, and is used in the form ofpropylene/α-olefin copolymer.

Packaging films formed from these known propylene/α-olefin copolymersare still not sufficient in heat-sealing properties, though they areexcellent in transparency and scratch resistance in comparison withthose formed from low density polyethylene, and accordingly it is hopedthat propylene/α-olefin copolymers excellent in heat-sealing propertieseven at lower temperatures will come to be obtained.

It is well known that the above-mentioned propylene/α-olefin randomcopolymers may be improved in heat-sealing properties by increasing theproportion of ethylene or α-olefin of 4 to 20 carbon atoms to propylenein the copolymer. However, if the proportion of ethylene or α-olefin of4 to 20 carbon atoms is increased in the copolymerization, the resultingpropylene/α-olefin copolymer increases in amount of the solvent-solublecomponent, whereby the resultant copolymers come to be poor inanti-blocking properties and also in stiffness.

Such propylene/α-olefin random copolymers excellent in heat-sealingproperties, anti-block properties and stiffness as mentioned above areavailable only when they have a low melting point in spite of the factthat the proportion of α-olefin in the copolymer is small.

Incidentally, olefin polymerization catalysts composed generally oftitanium compounds or vanadium compounds and organoaluminum compoundshave heretofore been used for preparing ethylene copolymers. In recentyears, however, catalysts composed of zirconium compounds andaluminoxane have been proposed of late as new Ziegler polymerizationcatalysts. Japanese Patent L-O-P Publn. No. 19309/1983 discloses aprocess for polymerizing ethylene and one or two or more C₃ -C₁₂α-olefins at a temperature of from -50° .C to 200° C. in the presence ofa catalyst composed of a transition metal containing compoundrepresented by the following formula

    (Cyclopentadienyl).sub.2 MeRHal

wherein R is cyclopentadienyl, C₁ -C₆ alkyl or halogen, Me is atransition metal, and Hal is halogen, and a linear aluminoxanerepresented by the following formula

    Al.sub.2 OR.sub.4 (Al (R)--O).sub.n

wherein R is methyl or ethyl, and n is a number of 4-20, or a cyclicaluminoxane represented by the following formula ##STR1## wherein R andn are as defined above. The publication cited above describes thatethylene should be polymerized in the presence of small amounts, up to10% by weight, of somewhat long chain α-olefins or mixtures thereof inorder to control a density of the resulting polyethylene.

Japanese Patent L-O-P Publn. No. 95292/1984 discloses an inventionrelating to a process for preparing a linear aluminoxane represented bythe foil.owing formula ##STR2## wherein n is 2-40, and R is C₁ -C₆alkyl, and cyclic aluminoxane represented by the following formula,##STR3## wherein n and R are as defined above. The publication citedabove describes that olefins are polymerized in the presence of thealuminoxane prepared by the process of said publication, for example,methyl aluminoxane in admixture with a bis(cyclopentadienyl) compound oftitanium or zirconium, whereupon at least twenty-five million g ofpolyethylene per 1 g of the transition metal per hour is obtained.

Japanese Patent L-O-P Publn. No. 35005/1985 discloses process forpreparing olefin polymerization catalysts, wherein an aluminoxanecompound represented by the following formula ##STR4## wherein R¹ is C₁-C₁₀ alkyl, and R⁰ is R¹ or represents --O-- by linkage therewith, isfirst allowed to react with a magnesium compound, the resulting reactionproduct is then chlorinated, followed by treating with a Ti, V, Zr or Crcompound. This publication cited above describes that the catalystsprepared by the process of said publication are particularly useful forthe copolymerizatlon of mixtures of ethylene and C₃ -C₁₂ α-olefins.

Japanese Patent L-O-P Publn. No. 35006/1985 discloses a combination of(a) mono-, di- or tri-cyclopentadienyl of two or more differenttransition metals or derivatives thereof and (b) aluminoxane as acatalyst system for preparing reactor blend polymers. Example 1 of theabove-cited publication discloses that polyethylene having a numberaverage molecular weight of 15,300, a weight average molecular weight of36,400 and containing 3.4% of the propylene component has been obtainedby polymerization of ethylene with propylene in the presence of acombination of bis (pentamethylcyclopentadienyl) zirconium dimethyl andaluminoxane as the catalyst. Example 2 of the said publication disclosespolymerization of ethylene with propylene in the presence of acombination of bis (pentamethylcyclopentadienyl) zirconlum dichloride,bis(methylcyclopentadienyl)zirconium dichloride and aluminoxane as thecatalyst, whereby a blend of polyethylene and ethylene/propylenecopolymer is obtained, said polyethylene having a number averagemolecular weight of 2,000, a weight average molecular weight of 8,300and the propylene content of 7.1 mol %, and comprising a toluene-solubleportion having a number average molecular weight of 2,200, a weightaverage molecular weight of 11,900 and the propylene content of 30 mol %and a toluene-insoluble portion having a number average molecular weightof 3,000, a weight average molecular weight of 7,400 and the propylenecontent of 4.8 mol %. Similarly, Example 3 of the said publicationdiscloses a blend of LLDP and an ethylene/propylene copolymer, saidLLDPE comprising a soluble portion having a molecular weightdistribution (Mw/Mn) of 4.57 and the propylene content of 20.6% and aninsoluble portion having the molecular weight distribution of 3.04 andthe propylene content of 2.9 mol %.

Japanese Patent L-O-P Publn. No. 35007/1985 discloses a process forpolymerizing ethylene alone or together with α-olefins of at least 3carbon atoms in the presence of a catalyst system containing metalloceneand a cyclic aluminoxane represented by the following formula ##STR5##wherein R is alkyl of 1-5 carbon atoms, and n is an integer of 1 toabout 20, or a linear aluminoxane represented by the following formula##STR6## wherein R and n are as defined above. According to time saidpublication, the polymers obtained by the above-mentioned process arealleged to have a weight average molecular weight of from about 500 toabout 1,400,000 and a molecular weight distribution of 1.5-4.0.

Japanese Patent L-O-P Publn. No. 35008/1985 discloses polyethylene orcopolymers of ethylene and C₃ -C₁₀ α-olefins, both having a broadmolecular weight distribution, obtained by using a catalyst systemcontaining at least two kinds of metallocenes and aluminoxane. The saidcopolymers disclosed in the above-mentioned publication are alleged tohave a molecular weight distribution (Mw/Mn) of 2-50.

Japanese Patent L-O-P Publn. No. 130314/1986 discloses polypropylenehigh in isotactlcity obtained by polymerization of propylene in tilepresence of a catalyst system comprising a sterically fixedzirconium-chelate compound and aluminoxane.

J. Am. Chem. Soc., 109, 6544 (1987) discloses formation of a highmolecular weight isotactic polyopropylene obtained by polymerization ofpropylene in the presence of a catalyst system comprisingethylenebis(indenyl)hafnium dichloride or its hydride and aluminoxane,said isotactic polypropylene having a narrow molecular weightdistribution (Mw/Mn) of 2.1-2.4.

Japanese Patent L-O-P Publn. No. 142005/1987 discloses a stereoblockpolypropylene having Mw/Mn of 5.0-14.9 obtained by polymerization ofpropylene in the presence of a catalyst system comprisingtetramethylethylenebis (cyclopentadienyl) titanium chloride andaluminoxane. The polypropylene thus obtained is short in isotactic chainlength and is a rubbery polymer.

The present inventors have come to accomplish the present invention onthe basis of their finding that ethylene copolymers which are small inMw/Mn and narrow in molecular weight distribution and, moreover, largein MFR₁₀ /MFR₂ and excellent in flowability are obtained bycopolymerizatlon of ethylene with α-olefins of 3-20 carbon atoms in thepresence of olefin polymerization catalysts composed of specific hafniumcompounds and organoaluminum oxy-compounds.

Furthermore, tile present inventors have found that when propylene andα-oleflns of 4-20 carbon atoms are copolymerized in the presence ofolefin polymerization catalysts composed of specific hafnium compoundsand aluminoxane, there are obtained propylene/α-olfein copolymers whichare narrow in molecular weight distribution and small in amount of theα-olefin copolymerized therewith, but are low in melting point incomparison with conventionally known propylene/α-olefin copolymers, onwhich the present invention has been based.

Accordingly, time present invention is to solve such problems associatedwith tile prior art as mentioned above, and an object of tile inventionis to provide ethylene copolymers which are small in Mw/Mn and narrow inmolecular weight distribution and, moreover, which are large in MFR₁₀/MFR₂ and excellent in flowability, and processes for preparing thesame.

A further object of the invention is to provide propylene/α-olefincopolymers which are narrow in molecular weight distribution and smallin amount of the α-olefin copolymerized therewith but have a low meltingpoint and, moreover, which are excellent in heat-sealing properties andalso excellent in anti-block properties and stiffness, and processes forpreparing the same.

Another object of the invention is to provide olefin polymerizationcatalysts, which produce polymers which are narrow in molecular weightdistribution in homopolymerization or narrow in molecular weight andcomposition distribution in copolymerization with high polymerizationactivities even bv the use of small amounts of aluminoxane, furthermore,produce easily polymers which are high in molecular weight.

DISCLOSURE OF THE INVENTION

The ethylene copolymers of the present invention are those laving (a)structural units derived from ethylene and (b) structural units derivedfrom α-olefin of 3-20 carbon atoms, which are characterized in that theyhave

(i) a density of 0.85-0.92 g/cm³,

(ii) an intrinsic viscosity [η] of 0.1-10 dl/g as measured in decalin(decahydronaphthalene) at 135° C.,

(iii) a (Mw/Mn) ratio of a weight average molecular weight (Mw) to anumber average molecular weight (Mn) of 1.2-4 as measured by GPC, and

(iv) a (MFR₁₀ /MFR₂) ratio of MFR10 under a load of 10 kg to MFR₂ undera load of 2.16 kg of 8-50 as measured at 190° C.

The processes for preparing ethylene copolymers of the present inventionare characterized in that ethylene and α-olefins of 3-20 carbon atomsare copolymerized so that a density of the resulting copolymers becomes0.85-0.92 g/cm³, in the presence of catalysts formed from

[A] hafnium compounds having multldentate coordination compounds asligands, in which at least two groups selected from among conjugatedcycloalkadienyl groups or substituted groups thereof are linked togethervia lower alkylene groups, or hafnium compounds obtained by treating theabove-mentioned hafnium compounds with alkylsilylated silica gel, and

[B] organoaluminum oxy-compounds.

The first propylene/α-olefin random copolymers of the present inventionare those having (a) structural units derived from propylene and (b)structural units derived from α-olefins of 4-20 carbon atoms, which arecharacterized in that they have

(i) 90-99 mol % of said structural units (a) and 1-10 mol % of saidstructural units (b),

(ii) an intrinsic viscosity [η] of 0.5-6 dl/g as measured in decalin(decahydronaphthalene) at 135° C.,

(iii) a melting point [Tm], as measured by a differential scanningcalorimeter, falling within the range of the formula 90<Tm<155-3.5(100-P) wherein P is the propylene component (mol %) contained in thecopolymer,

(iv) a (Mw/Mn) ratio of less than 3.5 between a weight average molecularweight (Mw) and a number average molecular weight (Mn) as measured byGPC, and

(v) a boiling trichloroethylene-insoluble matter in an amount of lessthan 5% by weight

The processes for preparing the first propylene/α-olefin copolymers ofthe present invention are characterized in that propylene and α-olefinsof 4-20 carbon atoms are copolymerized at a temperature of 40°-100° C.so that the resulting copolymers have 90-99 mol % of structural units(a) derived from propylene and 1-10% mol % of structural units (b)derived from the α-olefin, in the presence of catalysts formed from

[A] hafnium compounds having multidentate coordination compounds asligands, in which at least two groups selected from among conjugatedcycloalkadienyl groups or substituted groups thereof are linked togethervia lower alkylene groups, and

[B] organoaluminum oxy-compounds.

The second propylene/α-olefin random copolymers of the present inventionare those having (a) structural units derived from propylene, (b)structural units derived from ethylene and (c) structural units derivedfrom α-olefins of 4-20 carbon atoms, which are characterized in thatthey have

(i) 90-99 tool% of said structural units (a), 0.5-9.5 mol % of saidstructural units (b) and 0.5-9.5 mol % of said structural units (c),

(ii) an intrinsic viscosity [η] of 0.5-6 dl/g as measured in decalin at135° C.,

(iii) a melting point [Tm], as measured by a differential scanningcalorimeter, falling within the range of the formula 70<Tm<155-5.5(100-P) wherein P is the propylene component (mol %) contained in thecopolymer, and

(iv) a boiling trichloroethylene-insoluble matter in an amount of lessthan 5% by weight.

The processes for preparing the second propylene/α-olefin copolymers ofthe present invention are characterized in that propylene, ethylene andα-olefins of 4-20 carbon atoms are copolymerized so that the resultingcopolymers have 90-99 mol % of structural units (a) derived frompropylene, 0.5-9.5 mol % of structural units (b) and 0.5-9.5 mol % ofstructural units (c) , in the presence of catalysts formed from

[A] hafnium compounds having multidentate coordination compounds asligands in which at least two groups selected from among conjugatedcycloalkadienyl groups or substituted groups thereof are linked togethervia lower alkylene groups, and

[B] organoalumlnum oxy-compounds.

In accordance with the present invention, there are provided olefinpolymerization catalysts formed from

[A] hafnium compounds having multidentate coordination compounds asligands in which at least two groups selected from conjugatedcycloalkadienyl groups or substituted groups thereof are linked togerhervia lower alkylene groups,

[B] organoaluminum oxy-compounds, and

[C] organoaluminum compounds.

In accordance with the present invention, furthermore, there areprovided olefln polymerization catalysts formed from

[A] hafnium compounds having multidentate coordination compounds asligands in which at least two groups selected from among conjugatedcycloalkadienyl groups or substituted groups thereof are linked togethervia lower alkylene groups,

[B-1] organoaluminum oxy-compounds formed from tri-n-alkyl aluminum, and

[B-2] organoaluminum oxy-compounds in which at least one hydrocarbongroup other than n-alkyl group is bonded to Al atom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the process for the preparation of theolefln copolymers of the present invention.

FIG. 2 is a graph showing the relationship between the propylene contentand melting point of the propylene random copolymer of the presentinvention.

FIGS. 3-5 are stepwise illustrative of the method of evaluation ofheat-sealing properties of the propylene random copolymer of the presentinvention.

BEST MODE OF PRACTICING THE INVENTION

The ethylene copolymers of the present invention and processes forpreparing the same are illustrated below in detail.

The process for the preparation of the ethylene copolymers of thepresent invention is illustratively shown in FIG. 1

The ethylene copolymers of the invention are random copolymers ofethylene and α-oleflins of 3-20 carbon atoms. The ethylene copolymershave a density o.f 0.85-0.92 g/cm³, preferably 0.85-0.91 g/cm³ andespecially 0.85-0.90 g/cm³.

In this connection, the density of these ethylene copolymers wasmeasured by gradient tube density determination using the strand ofethylene copolymer used at the time of determining MFR₂ under a load of2.16 kg at 190° C.

In these ethylene copolymers, are present desirably structural units (a)derived from ethylene in an amount of 60-96 mol %, preferably 65-95tool% and especially 70-94 mol %, and structural units (b) derived fromα-olefin of 3-20 carbon atoms in an amount of 4-40 mol %, preferably5-35 mol % and especially 6-30 mol %.

The composition of the copolymer is determined by measuring a spectrumof ¹³ C-NMR of a specimen obtained by dissolving about 200 mg of thecopolymer in 1 ml of hexachlorobutadiene in a test tube of 10 mmφ underthe conditions of a measurement temperature of 120° C., measurementfrequency of 25.05 MHz, spectrum width of 1500 Hz, pulse repetition timeof 4.2 sec. and pulse width of 6 sec.

Alpha olefins of 3-20 carbon atoms used in the present invention includepropylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-l-pentene, 1-octene,1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene,1-eicosene, etc.

The ethylene copolymers of time present invention desirably have anintrinsic viscosity [η] of 0.1-10 dl/g, preferably 0.5-6 dl/g asmeasured in decalin at 135° C.

The molecular weight distribution (Mw/Mn) as obtained by gel permeationchromatography (GPC) of the ethylene copolymers of the invention is1.2-4, preferably 1.4-3.5 and especially 1.5-3.0. As is evidenced by theforegoing, the ethylene copolymers of time invention are narrow inmolecular weight distribution and excellent in anti-block properties.

In this connection, a value of (Mw/Mn) obtained in the invention wasdetermined by the following procedure in accordance with Takeuchi, "GelP erincation Chromatography, " Maruzen, Tokyo.

(1) Using a standard polystyrene having the known molecular weight (amonodispersed polystyrene produced and sold by Toyo Soda K.K.),molecular weight M and GPC (Gel Permeation Chromatography) count of thesample are measured to prepare a correlation diagram calibration curveof the molecular weight M and EV (Elution Volume). The concentration ofthe sample used is maintained at 0.02% by weight.

(2) GPC chromatograph of the sample is taken by GPC measurement, and anumber average molecular weight Mn and a weight average molecular:weight Mw, in terms of polystyrene, are calculated from the calibrationcurve mentioned in the above procedure (1) to obtain a value of Mw/Mn.In that case, the conditions under which the sample is prepared, and theconditions under which GPC measurement is conducted are as follows:

Preparation of sample

(a) The sample is put in an Erlenmeyer flask together witho-dichlorobenzene so that the same amounts to 0.1% by weight,

(b) The Erlenmeyer flask is heated at 140° C. and stirred for about 30minutes to dissolve the sample in o-dichlorobenzene.

(c) The solution is subjected to GPC.

GFC measurement condition

The measurement was conducted under the following conditions.

(a) Apparatus: 150C-ALC/GPC manufactured by Waters Co.

(b) Column: GMH Type manufactured by Toyo Soda K.K.

(c) Amount of sample: 400 μl

(d) Temperature: 140° C.

(e) Flow rate: 1 ml/min

In the ethylene copolymers of the invention, a (MFR₁₀ /MFR₂) ratio ofMFR₁₀ at 190° C. under a load of 10 kg to MFR₂ at 190° C. under a loadof 2.16 kg is 8-50 preferably 8.5-45 and especially 9-40.

Such ethylene copolymers having the MFR₁₀ /MFR₂ ratio falling within therange of 8-50 as mentioned above are quite favorable in flowability atthe time when they are melted.

In contrast thereto, the aforementioned known ethylene copolymers havingthe Mw/Mn ratio of 1.2-4 will come to have the MFR₁₀ /MFR₂ ratio in therange of 4-7, and hence they are poor in flowability at the time whenthey are melted.

As mentioned above, the ethylene copolymers of the present inventionhave such excellent characteristics that they have a small molecularweight distribution (Mw/Mn), and molded articles resulting therefrom areless sticky and, at the same time, they are large in MFR₁₀ /MFR₂ andexcellent in flowability at the time when they are melted.

The ethylene copolymers of the invention as illustrated above may beprepared by copolymerization of ethylene with α-olefins of 3-20 carbonatoms so that the resulting copolymers have a density of 0.85-0.92 g/cm³in the presence of catalysts formed from

[A] hafnium compounds having multidentate coordination compounds asligands in which at least two groups selected from among conjugatedcycloalkadienyl groups or substituted groups thereof are linked togethervia lower alkylene, or hafnium catalyst components obtained by treatingthe above-mentioned hafnium coinpounds with alkylsilylated silica gel,and

[B ] organoaluminum oxy-compounds.

The catalyst components [A] used in the invention are hafnium compoundshaving multidentate coordination compounds as ligands in which at leasttwo groups selected from among conjugated cycloalkadienyl groups orsubstituted groups thereof, e.g. indenyl group, substituted indenylgroup and partially hydrated compounds thereof, are linked together vialower alkylene groups, or compounds obtained by treating theabove-mentioned hafnium compounds with alkylsilylated silica gel.

The above-mentioned hafnium compounds include, for example, thefollowing compounds.

Ethylenehis (indenyl)dimethyl hafnium,

Ethylenebls (indenyl)diethyl hafnium,

Ethylenehis (indenyl)diphenyl hafnium,

Ethylenehis (indenyl)methyl hafnium monochloride,

Ethylenebis(indenyl)ethyl hafnium monochloride,

Ethylenebis(indenyl)methyl hafnium monobromide,

Ethylenebis(indenyl)hafnium dichloride,

Ethylenebis(indenyl)hafnium dibromide,

Ethylenebis(4,5, 6, 7-tetrahydro-1- indenyl)dimethyl hafnlum,

Ethylenehis (4,5, 6, 7-tetrahydro-1-indenyl)methyl hafnium monochloride,

Ethylenehis (4,5, 6, 7-tetrahydro-1-indenyl)hafnium dichloride,

Ethylenebis (4,5, 6, 7-tetrahydro- 1- indeny 1)hafnium dibromide,

Ethylenehis (4-methyl-1-indenyl)hafnium dichloride,

Ethylenehis (5-methyl-1-indenyl)hafuium dichloride,

Ethylenebis (6-methyl-1-indenyl)hafnium dichloride,

Ethylenebis (7-methyl-1-indenyl) hafnium dichloride,

Ethylenebis (5-methoxy-1-indenyl)hafnium dichloride,

Ethylenebis (2,3-dimethyl-1-indenyl)hafnium dichloride,

Ethylenehis (4,7-dimethyl-1-indenyl)hafnium (dichloride,

Ethylenebis (4,7-dimethoxy-1-indenyl)hafnium dichloride.

The above-mentioned hafnium compounds may contain small amounts ofzirconium or titanium. In such a case, the content of zirconurn ortitanium is less than 1% by weight, preferably less than 0.7% by weightand especially less than 0.5% by weight.

The hafnium catalyst components used in the present invention mayinclude compounds obtained by treating the above-mentioned hafniumcompounds with alkylsilylated silica gel. More particularly, the saidhafnium catalyst components may be hafnium compound solutions which areobtained, for example, by passing a solution of the above-mentionedhafnium compound in an organic solvent such as toluene through a columnpacked with alkylsilylated silica gel, wherein said hafnium compound isbrought into contact with the alkylsilylated silica gel.

The organic solvents used in that case are preferably aromatichydrocarbons such as toluene, benzene and xylene. The alkylsilylatedsilica gel used may include those obtained by treating silica gel withdimethyl dichlorosilane, ethylmethyl dichlorosilane, trimethylchlorosilane, trimethyl bromosilane, divinyl dichlorosilane, diethyldichlorosilane or methylpropyl dichlorosilane. The hafnium concentrationin the hafnium compound solution is usually from 1×10⁻⁵ to 5×10⁻³ mol/land the amount of the alkylsilylated silica gel used is usually 20-500 gper 1 mmol of the hafnium compound. A temperature at which the hafniumcompound solution is brought into contact with the alkylsilylated silicagel is usually 0°-50° C.

When the hafnium catalyst components obtained by treating theabove-mentioned hafnium compounds with the alkylsilylated silica gel areused as the catalyst components [A], ethylene copolymers excellent intransparency are obtained.

The catalyst components [B] used in the process of the present inventionare organoaluminum oxy-compounds. The organoaluminum oxy-compounds usedas the catalyst components may be shown as benzene-soluble aluminoxanesrepresented by the following general formulas (1) and (II). ##STR7##wherein R may be the same or different and is a hydrocarbon group suchas methyl, ethyl, propyl or butyl, preferably methyl or ethyl andespecially methyl, and m is an integer of at least 2, preferably atleast 5. The above-mentioned aluminoxanes may be prepared, for example,by the procedures as exemplified below.

(1) A procedure which comprises reacting a suspension in a hydrocarbonmedium of a compound containing water of absorption or a salt containingwater of crystallization, for example, magnesium chloride hydrate,copper sulfate hydrate, aluminumsulfate hydrate, nickel sulfate hydrateor serous chloride hydrate, with trialkylaluminum.

(2) A procedure which comprises reacting trialkylaluminum directly withwater, water vapor or ice in a medium such as benzene, toluene, ethylether and tetrahydrofuran.

The aluminoxanes as illustrated above may contain small amounts oforganometallic components.

Further, the organoaluminum oxy-compounds used in the present inventionmay be those which are insoluble in benzene. The benzene-insolubleorganoaluminum oxy-compounds are illustrated hereinafter.

The benzene-insoluble organoaluminum oxy-compounds used in the inventionmay be prepared by (i) reaction of organoaluminum compounds wlth wateror (ii) reaction of solutions of aluminoxane, for example, hydrocarbonsolutions thereof, with water or active hydrogen-containing compounds.

The benzene-insoluble organoaluminum oxy-compounds are considered tohave alkyloxyaluminum units represented by the formula ##STR8## whereinR¹ is hydrocarbon of 1˜12 carbon atoms and Al component soluble inbenzene at 60° C. is in an amount, in terms of A1 atom. of less than10%. preferably less than 5% and especially less than 2%, thus they areinsoluble or sparingly soluble in benzene.

Solubility in benzene of the organoaluminum oxy-compounds of the presentinvention is determined by suspending the organoaluminum oxy-compoundequivalent to A1 of 100 mg atom in 100 ml of benzene, stirring thesuspension at 60° C. for 6 hours, filtering the thus treated suspensionat a temperature elevated to 60° C. using G-5 glass filter equipped witha jacket, washing 4 times the solids portion separated on the filterwith 50 ml of benzene kept at 60° C. and then measuring the amount of A1atoms (×mmol) present in the total flitrate.

In the alkyloxyaluminum units mentioned above, R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, octyl, decyl,cyclohexyl, cyclooctyl, etc. Among these, preferred are methyl andethyl, particularly methyl.

In addition to the alkyloxyaluminum units of the formula ##STR9## thebenzene insoluble organoaluminum oxy-compounds of the invention maycontain oxyaluminum units represented by the formula ##STR10## In theabove-mentioned formulas, R¹ is as defined previously, R² is hydrocarbonof 1˜12 carbon atoms, alkoxyl of 1˜12 carbon atoms aryloxy of 6˜20carbon atoms, hydroxyl, halogen or hydrogen, and R¹ and R² represent thegroups different from each other. In that case, the benzene-insolubleorganoaluminum oxy-compounds are preferably those containing thealkyloxyaluminum units ##STR11## in the proportion of at least 30 mol %,preferably at least 50 mol % and especially at least 70 mol %.

The organoalumlnum compounds (i) used for preparing suchbenzene-insoluble organoaluminum oxy-compounds as mentioned above arethose represented by the formula R¹ _(n) AlX_(3-n) wherein R¹ ishydrocarbon of 1˜12 carbon atoms, X is halogen, alkoxyl of 1˜12 carbonatoms, aryloxy of 6˜20 carbon atoms or hydrogen, and n is 2˜3.

Such organoaluminum compounds (i) as mentioned above includetrialkylaluminum such as trimethylaluminum, triethylaluminum,tripropylaluminum, triisopropylaluminum, tri-n-butylalumlnum,tri-sec-butylaluminum, tri-tert-butylaluminum, tripentylaluminum,trihexylaluminum, trioctylaluminum, tridecylaluminum,tricyclohexylaluminum and tricyclooctylaluminum; dialkylaluminum halidessuch as dimethylaluminum chloride, dimethylaluminum bromide,diethylaluminum chloride, diethylaluminum bromide, anddiisobutylaluminum chloride; dialkylaluminum hydrides such asdiethylaluminum hydride and diisobutylaluminum hydride; dialkylaluminumalkoxides such as dimethylaluminum methoxide and diethylaluminumethoxide; and dialkylaluminum aryloxides such as diethylaluminumphenoxide. Of these organoaluminum compounds, preferred are those of theabove-mentioned general formula in which R¹ is alkyl and X is chlorine,and particularly preferred is trlalkylaluminum.

In this connection, isoprenylaluminum of the general formula (i-C₄H₉)_(x) Al_(y) (C₅ H₁₀)_(z) wherein x, y and z are each positiveinteger, and z≧2x may also used as the organoaluminum compound (i) .

The organoaluminum compounds (i) as illustrated above may be used eithersingly or in combination.

The active hydrogen-containing compounds (ii) used in preparing thebenzene-insoluble organoaluminum oxy-compounds of the present inventioninclude alcohols such as methyl alcohol and ethyl alcohol, and diolssuch as ethylene glycol and hydroquinone.

When water is used in preparing the benzene-insoluble organoaluminumoxy-compounds of tile present invention, the water may be used afterdissolving or suspending in hydrocarbon solvents such as benzene,toluene and hexane, ether solvents such as tetrahydrofuran, and aminesolvents such as triethylamine, or may be used in the form of watervapor or ice. As the water, moreover, there may also be used water ofcrystallization of salt such as magnesium chloride, magnesium sulfate,aluminum sulfate, copper sulfate, nickel sulfate, iron sulfate andcerrous chloride, or water of adsorption adsorbed to inoragnic compoundssuch as silica, alumina and aluminum hydroxide or polymers.

As mentioned above, the benzene-insoluble organoaluminum oxy-compoundsof the present invention may be prepared by reaction of theorganoaluminum compound (i) with water, or by reaction of a solution ofaluminoxane, for example, a hydrocarbon solution thereof, with water orthe active hydrogen containing compound. In preparing thebenzene-insoluble organoaluminum oxy-compound from the organoaluminumcompound and water, the organoaluminum compound is brought into contactwith water in a solvent, for example, a hydrocarbon solvent, and in thatcase, the water is added to the reaction system so that theorganoaluminum atoms dissolved in the reaction system become less than20% based on the total organoaluminum atom. In obtaining thebenzene-insoluble organoaluminum oxy-compounds according to theprocedure as mentioned above, it is desirable that the water is broughtinto contact with the organoaluminum compound in the proportion of 1˜5moles, preferably 1.5˜3 moles of the water to 1 mole of theorganoaluminum compound.

The above-mentioned reaction for forming the benzene-insolubleorganoaluminum oxy-compounds is carried out in solvents, for example,hydrocarbon solvents. The solvents used include aromatic hydrocarbonssuch as benzene, toluene, xylene, cumene and cymene, aliphatichydrocarbons such as butane, isobutane, pentane, hexane, octane, decane,dodecane, hexadecane and octadecane, alicyclic hydrocarbons such ascyclopentane, cyclooctane, cyclodecane and cyclododecane, suchhydrocarbon solvents, for example, petroleum fractions, as gasoline,kerosine and gas oil, halides of the above-mentioned aromatichydrocarbons, aliphatic hydrocarbons and alicycllc hydrocarbons,especially chlorides and bromides thereof, and ethers such as ethylether and tetrahydrofuran. Among these hydrocarbon media as exemplifiedabove, particularly preferred are aromatic hydrocarbons.

A concentration in terms of A1 atom of the organoaluminum compound inthe reaction system is desirably 1 ×10⁻³ to 5 gram atom/l preferably1×10⁻² to 3 gram atom/l, and a concentration in the reaction system ofwater such as water of crystallization is usually 1×10⁻³ to 20 mol/1,preferably 1×10⁻² to 10 mol/1. In that case, it is desirable that theorganoaluminum atoms dissolved in the reaction system are less than 20%,preferably less than 10% and especially in the range of from 0 to 5%based on the total organoaluminum atom.

Contact of the organoaluminum compound with water may be carried out,for example, by the following procedures.

(1) A procedure wherein a hydrocarbon solution of organoaluminum isbrought into contact with a hydrocarbon solvent containing water.

(2) A procedure wherein water vapor is blown into a hydrocarbon solutionof organoaluminum, thereby bringing the organoaluminum into contact withthe water vapor.

(3) A procedure wherein a hydrocarbon solution of organoaluminum ismixed with a hydrocarbon suspension of a compound containing water ofadsorption or a colnpound containing water of crystallization, therebybringing the organoaluminum into contact with the water of adsorption orwater of crystallization.

(4) A procedure wherein a hydrocarbon solution of organoaluminum isbrought into contact with ice.

The above-mentioned reaction of the organoaluminum with water is carriedout usually at a temperature of from -100 to 150° C., preferably -50 to100° C. and especially -30 to 80° C. The reaction time, though it maylargely vary depending upon the reaction temperature, is usually from 1to 200 hours, preferably 2 to 100 hours.

In preparing the benzene-insoluble organoalumlnum oxy-compounds from asolution of aluminoxane and water or a active hydrogen-containingcompound, the aluminoxane present in the solution of aluminoxane isbrought into contact with water or the active hydrogen-containingcompound.

The solution of aluminoxane is a solution of aluminoxane in such asolvent as used in forming the above-mentioned benzene-insolubleorganoaluminum oxy-compounds, preferably aromatic hydrocarbons such asbenzene and toluene, and this solution may contain dther components solong as they do not affect adversely the reaction between thealuminoxane and water or the active hydrogen-containing compound.

The amount of water or the active hydrogen-containing compound used inthe above-mentioned reaction is 0.1 to 5 moles, preferably 0.2 to 3moles based on 1 gram atom of aluminum present in the solution ofaluminoxane. A concentration in the reaction system of aluminoxane interms of aluminum atom is usually 1×10⁻³ to 5 gram atom/l, preferably1×10⁻² to 3 gram atom/1, and a concentration in the reaction system ofwater is usually 2×10⁻⁴ to 5 mole/1, preferably 2×10⁻³ to 3 mole/l.

Taking, as an example, the reaction of the solution of aluminoxane withwater, said solution of aluminoxane is brought into contact with wateror the active hydrogen-containing compound, for example, by thefollowing methods.

(1) A method which comprises bringing the solution of aluminoxane intocontact with a hydrocarbon solvent containing water.

(2) A method which comprises blowing water vapor into the solution ofaluminoxane, thereby bringing the aluminoxane present in the solution ofaluminoxane into contact with the water vapor.

(3) A method which comprises mixing the solution of aluminoxane with ahydrocarbon solution of a compound containing water of adsorption or acompound containing water of crystallization, thereby bringing thealuminoxane present in the solution of aluminoxane into contact with thewater of adsorption or water of crystallization.

(4) A method which comprises bringing the solution of aluminoxane intocontact directly with water or ice.

The above-mentioned procedures may also be applied to the case whereinthe active hydrogen-containing compound (ii) is used instead of water.

The reaction of the solution of aluminoxane with water or the activehydrogen-containing compound as illustrated above may be carried outusually at a temperature of from -50° to 150° C. preferably 0° to 120°C. and especially 20°˜100° C. The reaction temperature, though it maylargely vary depending upon the reaction temperature, is usually 0.5˜300hours, preferably about 1˜150 hours.

In preparing the ethylene copolymers by using the olefin polymerizationcatalysts as mentioned above, a concentration in the polymerizationsystem of the hafnium compound in terms of hafnium atom is usually 10⁻⁸to 10⁻² gram atom/l, preferably 10⁻⁷ to 10⁻³ gram atom/l.

The above-mentioned organoaluminum oxy-compounds are desirably used inan amount in terms of aluminum atom in present in the reaction system of10⁻⁴ to 10⁻¹ gram atom/l preferably 5×10⁻⁴ to 5×10⁻² gram atom/l.

The polymerization temperature employed is from -50° to 150° C.,preferably from 0° to 120° C.

The olefln polymerization mentioned above is carried out usually invapor phase or liquid phase. In the liquid phase polymerization, thesolvent used may be inert hydrocarbon, or the olefin itself may also beused as the solvent.

The hydrocarbon used in that case includes aliphatic hydrocarbons suchas butane, isobutane, pentane, hexane, heptane, octane, decane,dodecane, hexadecane and octadecane, alicyclic hydrocarbons such ascyclopentane, methylcyclopentane, cyclohexane and cyclooctane, aromatichydrocarbons such as benzene, toluene and xylene, and petroleumfractions such as gasoline, kerosine and gas oil.

The polymerization pressure employed is usually from ordinary pressureto 100 kg/cm², preferably from ordinary pressure to 50 kg/cm², and thepolymerization may be carried out batchwise, semi-continuously orcontinuously. A molecular weight of the resulting polymer may bemodified by the addition of hydrogen and/or by regulation of thepolymerization temperature employed.

Hereinafter, the first propylene/α-olefin random copolymers and processfor preparing the same of the present invention are illustrated indetail.

The propylene/α-olefin random copolymers of the present invention arerandom copolymers of propylene and α-oleflns of 4˜20 carbon atoms. Thepropylene/α-olefin random copolymers of the invention desirably containstructural units (a) derived from propylene in an amount of 90 99 mol %,preferably 92˜98 mol %, and structural units (b) derived from α-oleflnin an amount of 1˜10 mol %, preferably 2˜8 mol %. When the structuralunits (a) derived from propylene contained in the propylene/α-olefinrandom copolymer are less than 90 mol %, said copolymer tends to becomepoor in anti-blocking properties and stiffness and, on the other hand,when said units (a) are in excess of 99 mol %, said copolymer tends toincrease in melting point and become poor in heat-sealing properties.

α-oleflns of 4˜20 carbon atoms used herein include 1-butene, 1-pentene,1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octane, 1-decene,1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene.Among these, particularly preferred is 1-butene.

The propylene/olefin random copolymers of the present inventiondesirably have an intrinsic viscosity [η] of 0.5˜6 dl/g, preferably 1˜5dl/g as measured in decalin at 135° C. If this intrinsic viscosity isless than 0.5 dl/g, the copolymers tend to become poor in anti-blockingproperties and toughness and, on the other hand if said intrinsicviscosity exceeds 6 dl/g, the copolymers tend to become port inmoldability.

Further, the propylene/α-olefin random copolymers of the invention havea melting point [Tm] as measured by a differential scanning calorimeterfalling within the range of

    90<Tm<155-3.5 (100-P), preferably

    100<Tm<150-3.5 (100-P)

wherein P is the content (tool%) of propylene in the copolymer.

In FIG. 2, there is shown as a straight line A the schematicrelationship between the melting point Tm of the above-mentionedpropylene/α-olefin random copolymer and the propylene content (mol %)present in said copolymer. In this FIG. 2, there is also shown as astraight line B the relationship between the melting point Tm of theknown propylene/α-olefin random copolymer and the propylene content (mol%) present in said copolymer.

As is clear from FIG. 2, the melting point of the firstpropylene/α-olefin random copolymers of the present invention is lowerby 10°˜20° C. than that of the known propylene/α-olefin randomcopolymers when the amount of α-olefin copolymerized of the former isthe same as that of the latter. Accordingly, films obtained from thefirst propylene/α-olefin random copolymers of the invention areexcellent particularly in heat-sealing properties at low temperatures,and the films exhibit excellent heat-sealing properties even when theyhave small amounts of the copolymerized α-olefin, and hence they areexcellent in anti-blocking properties and have excellent stiffness.

In the present invention, the propylene/α-olefin random copolymer wasallowed to stand in a differential scanning calorimeter (DSC) at 200° C.for 5 minutes, cooled up to 20° C. at a rate of 10° C./min, and allowedto stand at 20° C. for 5 minutes, and then the temperature was elevatedfrom 20° C. to 200° C. at a rate of 10° C./min to obtain a temperature(Tm) at a maximum endothermic peak which was then taken as a meltingpoint of said propylene/α-olefln random copolymer.

The molecular weight distribution (Mw/Mn) of the firstpropylene/α-olefin random copolymers of the invention as obtained by gelpermeation chromatography (GPC) is less than 3.5, preferably less than3.0 and especially less than 2.5. As stated above, the firstpropylene/α-olefin random copolymers of the invention are narrow inmolecular weight distribution and, from this point, they have excellentanti-blocking properties.

The determination of melting point was conducted by using about 2.5 mgof the specimen and DSC of Perkin Elmer-7 Model at heat-up rate of 10°C./min.

The first propylene/α-olefin random copolymers of the invention aredesirably to have a soluble portion in boiling n-pentane in an amount ofless than 3% by weight, preferably less than 2% by weight and especiallyless than 1% by weight.

Further, the first propylene/α-olefin random copolymers of the inventionare desirably to have an insoluble portion in boiling trichloroethylenein an amount of less than 5% by weight, preferably less than 3% byweight and especially less than 1% by weight.

The amounts of the insoluble portion in boiling trichloroethylene andthe soluble portion in boiling n-pentane were determined by such amanner that about 3 g of the finely pulverized specimen was extractedfor 5 hours with 180 ml of each of the solvents in a cylindrical filterpaper by using a Soxhlet's extractor, and the extraction residue wasdried with a vacuum dryer until it reached a constant weight to obtainthe weight thereof, whereby a difference in weight between the driedresidue and the original specimen is calculated.

The first propylene/α-olefin random copolymers of the present inventionas illustrated above may be prepared by copolymerizing propylene andα-olefin of 4˜20 carbon atoms at a temperature of 40°˜100° C. so thatthe structural units (a) derived from propylene are present in an amountof 90˜99 mol % and the structural units (b) derived from α-olefin arepresent in an amount of 1˜10 mol %, in the presence of catalysts formedfrom

[A] hafnium compounds having as ligands multidentate compounds in whichat least two groups selected from among conjugated cycloalkadienylgroups or substituted groups thereof are linked together via loweralkylene groups, and

[B] organoaluminum oxy-compounds.

In that case, the copolymerizatlon may be carried out by employing thesame conditions as used in the preparation of the aforementionedethylene copolymers.

The first propylene/α-olefin random copolymers of the present inventionare excellent particularly in heat-sealing properties at lowtemperatures and hence are used as heat-sealing agents.

Hereinafter, the second propylene random copolymers and process forpreparing the same of the present invention are illustrated in detail.

The second propylene random copolymers of the invention are randomcopolymers of propylene, ethylene and α-olefins of 4˜20 carbon atoms. Inthe propylene random copolymers, the structural units (a) derived frompropylene are present in an amount of 90˜99 mol %. preferably 92˜98 mol%, the structural units (b) derived from ethylene in an amount of0.5˜9.5 mol %, preferably 1˜9 mol %, and the structural units (c)derived from α-olefin an an amount of 0.5˜9.5 mol %, preferably 1˜9 mol%. If the structural units (a) derived from propylene present in thesaid copolymers are less than 90 mol %, the copolymers tend to becomepoor in anti-blocking properties and stiffness. On the other hand, ifthe structural units (a) exceed 99 mol %, the copolymers tend toincrease in melting point and become poor in heat-sealing properties.

α-olefins of 4˜20 carbon atoms used herein include 1-butene, 1-pentene,1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octane, 1-decene,1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene.Among these, particularly preferred is 1-butene.

The second propylene random copolymers of the invention desirably havean intrinsic viscosity [η] as measured in decalin at 135° C. of 0.5˜6dl/g, preferably 1˜5 dl/g. If this intrinsic viscosity is less than 0.5dl/g, the copolymers tend to become poor in anti-blocking properties andtoughness and, on the other hand, if said intrinsic viscosity exceeds 6dl/g, the copolymers tend to become poor in moldability.

Further, the second propylene/α-olefin random copolymers of theinvention have a melting point [Tm] as measured by a differentialscanning calorimeter falling within the range of

    70<TM<155-5.5 (100-P), preferably

    90<Tm<150-5.5 (100-P)

wherein P is the content (mol %) of propylene in the copolymer.

The schematic relationship between the melting point Tm of theabove-mentioned propylene random copolymer and the propylene content(mol %) in said copolymer is the same as shown in FIG. 2.

In this manner, time melting point of the second propylene randomcopolymers is lower by 10°˜20° C. than that of the knownpropylene/αoleflin random copolymers when the amounts of ethylene andα-olefln copolymerized of the former are the same as those of thelatter. Accordingly, films obtained from the second propylene randomcopolymers of the invention are excellent particularly in heat-sealingproperties at low temperatures, and the films exhibit excellentheat-sealing properties even when they have small amounts of ethyleneand α-olefin copolymerized, and hence they are excellent inanti-blocking properties and have excellent stiffness.

Further the molecular weight distribution (MwMn) of the second propylenerandom copolymers of the invention as obtained by gel permeationchromatography (GPC) is less than 3.5, preferably less than 3.0 andespecially less than 2.5. As stated above, the second propylene randomcopolymers of the invention are narrow in molecular weight distributionand, from this point, they have excellent anti-blocking properties.

The second propylene random copolymers of the invention are desirably tohave a soluble portion in boiling n-pentane in an amount of less than 5%by weight, preferably less than 3% by weight and especially less than 2%by weight.

Furthermore, the second propylene random copolymers of the invention aredesirably to have an insoluble portion in boiling trichloroethylene inan amount of less than 5% by weight, preferably less than 3% by weightand especially less than 1% by weight.

The second propylene random copolymers of the present invention asillustrated above may be prepared by copolymerizlng propylene, ethyleneand α-oleflns of 4˜20 carbon atoms at a temperature of 40°˜100° C. sothat the structural units (a) derived from propylene are present in anamount of 90˜99 mol% in the resulting copolymers, the structural units(b) derived from ethylene in an amount of 0.5˜9.5 mol%, and thestructural units (c) derived from (α-olefin in an amount of 0.5˜9.5 mol%, in the presence of catalysts formed from

[A] hafnium compounds having as ligands multidentate compounds in whichat least two groups selected from among conjugated cycloalkadienylgroups or substituted groups thereof are linked together via loweralkylene groups, and

[B] organoaluminum oxy-compounds.

In that case, the copolymerization may be carried out by employing thesame conditions as used in the preparation of the aforementionedethylene copolymers.

The second propylene random copolymers of the invention as illustratedabove are excellent particularly in heat-sealing properties at lowtemperatures, and hence are used as heat-sealing agents.

Hereinafter, the first olefin polymerization catalysts of the presentinvention are illustrated in detail.

The first olefin polymerization catalysts of the invention are formedfrom

[A] hafnium compounds having as ligands multidentate compounds in whichat least two groups selected from among conjugated cycloalkadienylgroups or substituted groups thereof are linked together via loweralkylene groups,

[B] organoaluminum oxy-compounds, and

[C] organoaluminum compounds.

In the olefin polymerization catalyst mentioned above, the hafniumcompounds [A] are organoaluminum oxy-compounds [B] used may be the sameas those mentioned previously.

The organoaluminum compounds [C] used herein may be those having in themolecule at least one Al--C bond, for example, the compounds asmentioned below.

That is, (i) organoaluminum compounds represented by the general formula(R¹)_(m) Al(OR²)_(n) H_(p) X_(q) wherein R¹ and R², which may be thesame or different, are each hydrocarbon of usually 1 to 15 carbon atoms,preferably 1 to 10 carbon atoms, X is halogen, m is 1≦m≦3, n is 0≦n≦2, pis 0≦p≦2, and q is 0≦q≦2, and m+n+p+q=3, and (ii) alkylated complexcompounds of metals of Group 1 of the periodic table and aluminumrepresented by the general formula M¹ Al(R¹)₄ wherein M¹ is Li, Na or K,and R¹ is as defined above.

Of the organoaluminum compounds mentioned above, particularly preferredare those having hydrocarbon groups other than n-alkyl group.Hyydrocarbon groups other than n-alkyl group may include alkyl having abranched chain such as isoalkyl, cycloalkyl and aryl. The organoaluminumcompounds as illustrated above may include, for example,trialkylaluminum such as triisopropyalumlnum, triisobutylaluminum,tri-2-methylbutylaluminum, tri-3-methylbutylaluminum,tri-2-methylpentylaluminum, tri-3-methylpentylaluminum,tri-4-methylpentylaluminum, tri-2-methylhexylaluminum,tri-3-methylhexylaluminum and tri-2-ethylhexylaluminum;tricycloalkylaluminum such as tricyclohexylaluminum; triarylaluminumsuch as triphenylaluminum and tritolylaluminum; dialkylalumlnum hydridessuch as diisobutylaluminum hydride; and alkylaluminum alkoxides such asisobutylaluminum methoxide, isobutylaluminum ethoxlde andisobutylaluminum isopropoxide. Of these organoaluminum compounds,preferred are those having branched alkyl groups, particularlytrialkylaluminum compounds. Furthermore, isoprenylaluminum representedby the general formula (i-C₅ H₉)_(x) Al_(y) (C₅ H₁₀)_(z) wherein x, yand z are each a positive integer, and z≧2x, is also useful. Compoundscapable of forming the above-mentioned organoaluminum compounds in thepolymerization system, for example, halogenated aluminum and alkyllithium, or halogenated aluminum and alkyl megnesium, may be added tothe polymerization system.

In polymerizlng olefin by using the first olefin polymerizationcatalysts of the present invention, the hafnium compound [A] isdesirably used in an amount, in terms of hafnium atoms present in thepolymerization reaction system, of 10⁻⁸ ˜10⁻² gram atom/1, preferably10⁻⁷ ˜10⁻³ gram atom/1, the organoaluminum oxy-compound [B] is desirablyused in an amount, in terms of aluminum atoms present in thepolymerization reaction system, of less than 3 mg atom/1, preferably0.01˜2 mg atom/1 and especially 0.02˜1 mg atom/1, and the organoaluminumcompound [C] is desirably used in such an amount that the proportion ofaluminum atoms derived from said organoaluminum compound [C] in thereaction system to the total aluminum atoms of the organoaluminumoxy-compound [B] and organoaluminum compound [C] is 20˜99%, preferably25˜98% and especially 30˜95%.

In the reaction system, the ratio of the total aluminum atom of theorganoaluminum oxy-compound [B] and organoaluminum compound [C] tohalfnium atoms of the hafnium compound [A] is usually 20˜10000,preferably 50˜5000 and especially 100˜2000.

The olefln polymerization may be carried out by employing the samecondition as used in the preparation of ethylene copolymers asaforesaid.

Hereinafter, the second olefin polymerization catalysts of the presentinvention are illustrated in detail.

The second olefin polymerization catalysts of the invention are formedfrom

[A] hafnium compounds having as ligands multidentate compounds in whichat least two groups selected from among conjugated cycloalkadienylgroups or substituted groups thereof are linked together via loweralkylene groups,

[B-1] organoaluminum oxy-compounds formed from tri-n-alkylaluminum, and

[B-2] organoaluminum oxy-compounds in which at least one hydrocarbongroup other than n-alkyl is linked to Al atom.

In the olefin polymerization catalysts mentioned above, the hafniumcompounds [A] used are the same as those mentioned previously.

The catalyst components [B-1] used in the second olefin polymerizationcatalysts of the invention are organoaluminum oxy-compounds formed fromtri-n-alkylaluminum.

n-alkyl group in the tri-n-alkylaluminum mentioned above includesmethyl, ethyl, n-propyl, n-butyl, n-octly and n-decyl. Among these,particularly preferred is methyl.

The catalyst components [B-2] used in the second olefin polymerizationcatalysts of the invention are organoaluminum oxy-compounds in which atleast one hydrocarbon group other than n-alkyl is linked to Al atom.

The hydrocarbon group other than n-alkyl includes alkyl having branchedchain such as isoalkyl, cycloalkyl and aryl.

The above-mentioned organoaluminum oxy-compounds [B-2] in which at leastone hydrocarbon group other than n-alkyl is linked to Al atom may beformed from organoaluminum compounds in which at least one hydrocarbongroup other than n-alkyl is linked to Al atom. Such organoaluminumcompounds as used in the above case include, for example,trialkylaluminum such as triisopropylaluminum, triisobutylaluminum,tri-2-methylbutylaluminum, tri-3-methylbutylaluminum,tri-2-methylpentylaluminum, tri-3-methylpentylaluminum,tri-4-methylpentylaluminum, tri-2-methylhexylaluminum,tri-3-methylhexylaluminum and tri-2-ethylhexylaluminum;tricycloalkylalumlnum such as tricyclohexylaluminum; triarylaluminumsuch as trlphenylaluminum and tritolylaluminum; dialkylaluminum hydridessuch as diisobutylaluminum hydride; and alkylaluminum alkoxides such asisobutylaluminum methoxide, isobutylaluminum ethoxide andisobutylaluminum isopropoxide. Of these organoaluminum compounds,preferred are those having branched alkyl groups, particularlytrialkylaluminum compounds. Furthermore, isoprenylaluminum representedby the general formula i-C₄ H₉)_(x) Al_(y) (C₅ H₁₀)_(z) wherein x, y andz are each a positive integer, and z≧2x, is also useful.

In polymerization olefin by using the second olefin polymerizationcatalysts of the present invention, the hafnium compound [A] isdesirably used in an amount, in terms of hafnium atoms present in thepolymerization reaction system, of 10⁻⁸ 10⁻² gram atom/l , preferably10⁻⁷ 10⁻³ gram atom/l, the organoaluminum oxy-compound [B-1] in anamount, in terms of aluminum atoms in the polymerization reactionsystem, of less than 3 mg atom/l, preferably 0.01˜2 mg atom/1 andespecially 0.02˜1 mg atom/l, and the organoaluminum oxy-compound [B-2]in such an amount that the proportion of aluminum atoms derived from theorganoaluminum oxy-compound [B-2] in the reaction system to the totalaluminum atom of the organoaluminum oxy-compound [B-1] andorganoaluminum oxy-compound [B-2] is 20˜95%, preferably 25 ˜90% andespecially 30˜85%.

In the reaction system, the ration of the total aluminum atom of theorganoaluminum oxy-compound [B-1] and organoaluminum oxy-compound [B-2]to hafnium atoms of the hafnium compound [B] is usually 20˜10000,preferably 50˜5000 and especially 100˜2000.

In that case, the olefin polymerization may be carried out by employingthe same conditions as used in the preparation of ethylene copolymers asaforesaid.

EFFECT OF THE INVENTION

Novel ethylene copolymers of the present invention are small in Mw/Mnand narrow in molecular weight distribution and, moreover, large inMFR₁₀ /MFR₂ and excellent in flowability, Accordingly, the ethylenecopolymers of the invention have excellent processability and areexcellent in anti-blocking properties and the like properties.

Novel propylene copolymers of the invention are low in melting point incomparison with known propylene/α-olefin random copolymers even whensaid novel propylene copolymers are low in α-olefin content, and hencethey have excellent anti-blocking properties and stiffness. In thepresent invention, there are also provided processes for preparing thesenovel copolymers mentioned above readily and efficiently.

The olefin polymerization catalysts of the invention exhibit highactivities even when relatively small amounts of organoaluminumoxy-compounds are used therein, and by the use of said catalysts, olefinpolymers large in molecular weight and narrow in molecular weightdistribution and composition distribution are obtained.

The present invention is illustrated below with reference to examples,but it should be construed that the invention is in no way limited tothose examples.

EXAMPLE 1 Preparation of ethylene copolymer Preparation ofmethylaluminoxane

Methylaluminoxane was prepared in accordance with the proceduredescribed in Polymer Commun., 29, 180 (1988).

Synthesis of ethylenebis(indenyl)hafnium dichloride

A nitrogen-purged 200 ml glass flask was charged with 5.4 g ofbis(indenyl)ethane [synthesized on the basis of Bull. Soc. Chim., 2954(1967)] and 50 ml of THF, and the flask was cooled with stirring to-30°˜40° C. To the flask was added dropwise 31.5 ml of n-Bu Li (1.6 Msolution), stirred successively at -30° for 1 hours, and the temperaturewas elevated spontaneously to room temperature, thereby anionizing thebis(indenyl)ethane. Separately, a nitrogen-purged 200 ml glass flask wascharged with 60 ml of THF, and the flask was cooled to below -60° C.followed by gradual addition of 6.7 g of HfCl₄ (contained 0.78% byweight of zirconium atoms as contaminants). Thereafter, the flask washeated-up to 60° C. and stirred for 1 hour. To the flask was addeddropwise the anionized ligand, and stirred at 60° C. for 2 hours,followed by filtration with a glass filter. The liltrate wasconcentrated at room temperature to about 1/5 of the original volume. Bythis operation, solids were separated. The separated solids werefiltered with a glass filter, followed by washing with hexane/ethylether and vacuum drying to obtain ethylenehis (indenyl)hafniumdichloride.

The hafnium compound thus obtained contained 0.40% by weight ofzirconium atoms.

Poyolymerization

A thoroughly nitrogen-purged 2 liter glass flask was charged with 950 mlof toluene and 50 ml of 1-octene, and ethylene gas was passedtherethrough at a rate of 160/l hr. The temperature in the system waselevated to 55° C., and 1.88 mmoles in terms of aluminum atom ofmethylaluminoxane and 7.5 ×10⁻³ mmole of ethylenebis(indenyl)hafniumdichloride were added to the system to initiate polymerization. Thepolymerization was carried out at 60° C. for 10 minutes underatmospheric pressure while continuously feeding ethylene gas. Thepolymerization was stopped by the addition of small amounts of methanol,and the polymerization solution obtained was poured in large amounts ofmethanol to separate polymer. The separated polymer was dried at 130° C.for 12 hours under reduced pressure to obtain 23.2 g of a polymer havinga density of 0.866 g/cm³, the ethylene content of 81.3 mol%, [η] of 1.71dl/g, Mw/Mn of 2.59, MFR₂ of 2.12 g/10 min and MFR₁₀ /MFR₂ ratio of13.1.

EXAMPLE 2

A thoroughly nitrogen-purged 2 liter glass flask was charged with 1liter of toluene, and a mixed gas of ethylene and propylene (140 1/hrand 40 1/hr respectively) was passed therethrough. The temperature inthe system was elevated to 75° C., and 1.88 mmoles in terms of aluminumatom of methylaluminoxane and 7.5×10⁻³ mmol ofethylenebis(indenyl)hafnium dichloride were added to the system toinitiate polymerization. The polymerization was carried out at 80° C.for 10 minutes under atmospheric pressure while continuously feeding theabove-mentioned mixed gas to the system. Thereafter, the operation wasconducted in the same manner as in Example 1 to obtain 17.5 g of apolymer having a density of 0.887 g/cm³, the ethylene content of 84.0mol %, [η] of 1.50 dl/g, Mw/Mn of 2.50, MFR₂ of 0.80 g/10 min and MFR₁₀/MFR₂ ratio of 12.7.

COMPARATIVE EXAMPLE 1

A copolymer of ethylene and propylene (prepared by using a catalystcomposed of VOCl₃ and aluminum ethyl sesquichloride) having a density of0 87 g/cm³ MFR₂ of 2 9 g/10 min and Mw/Mn of 2.16 was found to haveMFR₁₀ /MFR₂ ratio of 5.90.

EXAMPLE 3 Preparation of hafnium catalyst

A glass column of 35 mm in inside diameter was filled with a suspensionin toluene of 40 g of dimethylsilylated silica gel (Art. 7719, a productof MERCK) deaerated at room temperature for 4 hours. Subsequently, 200ml of the toluene solution (Hf=2.07 mmol/l) ofethylenebis(indenyl)hafnium dichloride prepared in Example 1 wasgradually poured into the column. A hafnium solution (Hf=0.17 m mol/l)eluted by this operation was used as a catalyst component.

Polymerization

The polymerization was carried out in the same manner as in Example 1except that tile polymerization was carried out at 70° C. for 35 minutesusing 6.6×10⁻³ mg atom of hafnium atom, to obtain 42.2 g of a colorlesstransparent polymer having a density of 0.855 g/cm³, the ethylenecontent of 76.2 mol %, [η] of 1.89 dl/g, Mw/Mn of 2.48, MFR₂ of 1.49g/10 min and MFR₁₀ /MFR₂ ratio of 10.1.

EXAMPLE 4

The polymerization was carried out in the same manner as in Example 2except that the hafnium catalyst component prepared in Example 3 wasused in an amount of 6.6×10⁻³ mg atom in terms of hafnium atom to obtain17.0 g of a colorless transparent polymer having a density of 0.883g/cm³, the ethylene content of 83.5 tool%, [η] of 1.61 dl/g, Mw/Mn of2.54, MFR₂ of 0.73 g/10 min, and MFR₁₀ /MFR₂ ratio of 12.2.

EXAMPLE 5

The polymerization was carried out in the same manner as in Example 1except that tile polymerization temperature employed was 40° C. and thepolymerization time employed was 15 minutes to obtain 20.5 g of apolymer having a density of 0.868 g/cm³ the ethylene content of 82 0 mol% [η] of 1.79 dl/g, Mw/Mn of 2.81, MFR₂ of 0.90 g/10 min and MFR₁₀ /MFR₂ratio of 32.0.

EXAMPLE 6 Preparation of propylene copolymer Polymerization

A thoroughly nitrogen-purged 2 liter stainless steel autoclave wascharged at room temperature with 500 ml of toluene, 3 moles ofpropylene, 0.1 mole of 1-butene and 5 mg atom in terms of Al atom ofmethylaluminoxane. The temperature in the polymerization system waselevated to 45° C., and 1.25×10⁻³ mmole of theethylenebis(indenyl)hafnium dichloride obtained in Example 1 was addedto the system to carry out polymerization at 50° C. for 0.5 hours. Thepolymerization was stopped by the addition of methanol to thepolymerization system.

The polymer slurry obtained was poured into large amounts of methanol,the slurry was recovered by filtration and washed with an tsobutylalcohol/hydrochloric acid solution to remove the catalyst componentstherefrom. The recovered slurry was then vacuum dried overnight at 80°C. and 200˜300 mmHg to obtain 27.5 g of a polymer having the 1-butenecontent of 2.2 mol%, [η] of 3.02 dl/g as measured in decalin at 135° C.,a melting point of 124° C. as measured by DSC, a boilingtrichloroethylene-insoluble content of 0% by weight, boilingn-pentane-soluble content of 0.3% by weight and Mw/Mn of 2.41 asmeasured by GPC.

EXAMPLE 7

The polymerization was carried out in the same manner as in Example 6except that the amount of 1-butene charged was changed to 0.25 mol toobtain 29.1 g of a polymer having the 1-butene content of 5.6 mol%, [η]of 2.95 dl/g, a melting point of 116° C., a boilingtrichloroethylene-insoluble content of 0% by weight, a boilingn-pentane-soluble content of 0.4% by weight and Mw/Mn of 2.33.

EXAMPLE 8 Polymerization

A mixed gas composed of 96.7 mol % of propylene, 2.1 mol % of 1-buteneand 1.2 tool% of ethylene was prepared.

A thoroughly nitrogen-purged 2 liter stainless steel autoclave wascharged with 500 ml of toluene and then cooled to 0° C. and theautoclave was further charged with 3 moles of the mixed gas preparedabove and 5 mg atom in terms of A1 atom of methylaluminoxane. Thetemperature in the polymerization system was elevated to 45° C., and1.25×10⁻³ m mole of the ethylenebis(indenyl)hafnium dichloride obtainedin Example 1 was added to the system to initiate polymerization at 50°C. for 0.5 hours. The polymerization was stopped by the addition ofmethanol to the polymerization system. The polymer slurry obtained waspoured into large amounts of methanol, the slurry was recovered byfiltration and washed with an isobutyl alcohol/hydrochloric acidsolution to remove the catalyst components therefrom. The recoveredpolymer was then vacuum dried overnight at 80° C. and 200˜300 mmHg toobtain 51.3 g of a polymer having the 1-butene content of 1.4 mol %, theethylene content of 1.1 mol %, [η] of 3.32 dl/g as measured in decalinat 135° C., a melting point of 121° C. as measured by DSC, a boilingtrichloroethylene-insoluble content of 0% by weight, boilingn-pentane-soluble content of 0.9% by weight and Mw/Mn of 2.45 asmeasured by GPC.

EXAMPLE 9

The polymerization was carried out in the same manner as in Example 8except that the mixed gas composed of 95.1 mol % of propylene, 3.9 mol %of 1-butene and 1.0 mol % of ethylene was used to obtain 48.5 g of apolymer having the 1-butene content of 2.7 mol %, the ethylene contentof 0.8 mol %, [η] of 3.29 dl/g, a melting point of 118° C., a boilingtrichloroethylene-insoluble content of 0% by weight, a boilingn-pentane-soluble content of 1.1% by weight and Mw/Mn of 2.40.

EXAMPLE 10 Polymerization

A thoroughly nitrogen-purged 2 liter stainless steel autoclave wascharged with 750 ml of toluene and then saturated with propylene gas. Tothe autoclave were added 7.5 mg atom in terms of A1 atom ofmethylaluminoxane and 1.88 ×10⁻³ mmole of theethylenebls(indenyl)hafnium dichloride. Polymerization was carried outat 50° C. for 0.5 hour at the total pressure of 7 kg/cm² G whilecontinuously feeding propylene gas to the autoclave. The polymerizationwas stopped by the addition of methanol to the polymerization system.The polymer slurry obtained was poured into large amounts of methanol,the slurry was recovered by filtration and washed with an isobutylalcohol/hydrochloric acid solution to remove the catalyst componentstherefrom. The recovered slurry was then vacuum dried overnight at 80°C. and 200˜300 mmHg to obtain 107.1 g of an isotactic polypropylenehaving Mw/Mn of 1.89 as measured by GPC, a melting point of 132° C. asmeasured by DSC, [η] of 2.82 dl/g as measured in decalin at 135° C., aboiling trichloroethylene-insoluble content of 0% by weight and aboiling n-pentane-soluble content of 0.2% by weight.

EXAMPLE 11

A mixed gas composing 98.5 mol % of propylene gas and 1.5 mol % ofethylene gas was prepared. The operation subsequent thereto was carriedout in the same manner as in Example 6 to obtain 53.3 g of a polymerhaving the ethylene content of 1.3 mol % [η] of 3 50 dl/g, a meltingpoint of 125° C., a boiling trichloroethylene-insoluble content of 0% byweight, a boiling n-pentane-soluble content of 1.0% by weight and Mw/Mnof 2.39.

Evaluation

Heat-sealing properties of the propylene polymers obtained hereinabovewere evaluated in the following manner.

Preparation of film

On a press plate were placed an aluminum sheet of a 0.1 mm thick, apolyester sheet (a product sold under a trade name of Rumiler by Toray)and a polyimide resin sheet (a product sold under a trade name of Captonby Du Pont), a square of 15 cm×15 cm of the center of which had been cutoff, in that order, and 0.8 g of the specimen was placed in this center(the cut-off portion of the polyimide resin sheet), and then Rumtler®,an aluminum sheet and a press plate were superposed thereon in thatorder (see FIG. 3).

The specimen thus interposed between the press plates was placed in ahot press kept at 200° C. and preheated for about 5 minutes, followed bysubjecting three times to pressure application (20 kg/cm² G) and releaseoperation in order to remove air bubbles present in the specimen.Subsequently, the pressure was increased finally to 150 kg/cm² G and thespecimen was leated for 5 minutes under pressure. After releasing thepressure, the press plate was taken out from a press machine andtransferred to separate press machine kept at 30° C. in its press inportion and then cooled for 4 minutes at a pressure of 100 kg/cm²followed by releasing the pressure and taking out the specimentherefrom. Of the films thus obtained, those having a uniform thicknessof 50˜70 μm were used as the films for measurement.

Measurement of heat-sealing strength

The films thus prepared are placed for 2 days in a hygrostat kept at 50°C. (aging). In practicing the aging, sheets of paper are applied to bothsides of the film so that the films do not come in contact with eachother. The films thus aged are cut up into strips of a 15 mm thick, andtwo sheets of the strip are placed one upon another and then interposedbetween two sheets of Teflon Film of a 0.1 mm thick, followed by heatsealing. The heat sealing is carried out while maintaining thetemperature of a lower portion of a hot plate of heat sealer constant at70° C. and varying only the temperature of an upper portion of hot platesuitably at intervals of 5° C. The heat-sealing pressure employed is 2kg/cm² the lieat-sealing time employed is 1 second, and a width of heatseal is 5 mm (accordingly a sealed area is 15 mm×5mm).

Heat-sealing strength is determined by obtaining a peeling strength ofthe heat sealed film subjected to peeling test at a rate of 30 cm/min ateach heat-sealing temperature as mentioned above. (See FIG. 4.)

Following the above-mentioned procedure, a peeling strength at each ofthe heat-sealing temperatures preset at interval of 5° C. is obtained,and the plots of heat-sealing temperature-peeling strength are connectedby means of a curved line. On the basis of the curved line, a heatsealing temperature corresponding to a peeling strength of 800 g /15 mmis taken as a completely heat-sealed temperature (see FIG. 5).

Table 1 below shows completely heat-sealed temperatures of the propylenepolymers obtained in the foregoing examples.

                  TABLE 1                                                         ______________________________________                                                    Example                                                                       6    7      8       9    10   11                                  ______________________________________                                        Completely heat-sealed                                                                      134    125    117   122  120  127                               temperature (°C.)                                                      ______________________________________                                    

EXAMPLE 12 Preparation of organoaluminum oxy-compound [B-1]

A thoroughly nitrogen-purged 400 ml flask was charged with 37 g of Al₂(SO₄)₃.14H₂ O and 125 ml of toluene and cooled to 0° C., followed bydropwise addition of 500 mmol of trimethylaluminum diluted with 125 mlof toluene. The temperature of the flask was elevated to 40° C., andreaction was continued at that temperature for 10 hours. After thecompletion of the reaction, solid-liquid separation of the reactionmixture was effected by filtration, and the toluene was removed from thefiltrate to obtain 13 g of a white solid organoaluminum oxy-compound.The molecular weight of the compound obtained was 930 as measured inbenzene by the cryoscopic method, and m value shown in the catalystcomponent ]B-1] was 14.

Polymerization

A thoroughly nitrogen-purged 2 liter stainless steel autoclave wascharged with 500 ml of toluene, and the system was purged with propylenegas. Successively, to the autoclave were added 1 mmol oftriisobutylaluminum, 1 mg atom in terms of Al atom of the organoaluminumoxy-compound obtained above, and 1×10⁻³ mmol of theethylenebis(indenyl)hafnium dichloride obtained in Example 1, and thetemperature of tile system was elevated to 45° C., Thereafter,polymerization was carried out at 50° C. for 1 hours, while feedingpropylene gas to the polymerization system so that the total pressurebecame 7 kg/cm² G, to obtain 45.0 g of an isotactic polypropylene having[η]]of 2.5 dl/g as measured in decalin at 135° C., Mw/Mn of 2.2, amelting point of 132° C., a boiling trichloroethylene-insoluble contentof 0% by weight and a boiling n-pentane-soluble content of 0.2% byweight.

COMPARATIVE EXAMPLE 2

The polymerization of Example 12 was repeated except that thetriisobutylaluminum was not used to obtain 5.1 g of isotacticpolypropylene having [η] of 1.9 dl/g, Mw/Mn of 2.1 and a melting pointof 131° C.

EXAMPLE 13

The polymerization of Example 12 was repeated except that in place ofthe triisobutylaluminum there were used 1 m mol oftri-2-ethylhexylaluminum and 0.5 mg atom in terms of A1 atom ofcommercially available aluminoxane to obtain 38.2 g of isotacticpolypropylene having [η] of 2.3 dl/g, Mw/Mn of 2 4, a melting point of131° C., a boiling trichloroethylene-insoluble content of 0% by weightand a boiling n-pentane-soluble content of 0.3% by weight.

EXAMPLE 14

A nitrogen-purged 1 liter glass autoclave was charged with 335 ml oftoluene and 15 ml of octene, followed by elevating the temperature oftime system to 70° C. while blowing ethylene gas thereinto.Successively, to the autoclave were added 0.4 mmol oftriisobutylaluminum, 0.2 mg atom in terms of Al atom of commerciallyavailable aluminoxane and 3×10⁻³ mmol of tile ethylenehis (indenyl)hafnium dichloride obtained in Example 1 to initiate polymerization. Thepolymerization was carried out at 70° C. for 30 minutes whilecontinuously feeding ethylene gas to the polymerization system to obtain16.8 g of an ethylene/1-octene copolymer having Mw/Mn of 3.18, MFR₂ of0.09 g/10 min, MFR₁₀ /MFR₂ of 30.7 and a density of 0.879 g/cm³.

EXAMPLE 15 Preparation of organoaluminum oxy-compound [B-2]

A thoroughly nitrogen-purged 400 ml flask was charged with 4.9 of Al₂(SO₄)₃.14H₂ O and 125 ml of toluene and cooled to 0° C., followed bydropwise addition of 200 mmol of triisobutylaluminum diluted with 125 mlof toluene. The temperature of the reaction system was elevated to 40°C., and reaction was continued at that temperature for 24 hours. Afterthe completion of the reaction, solid-liquid separation of the reactionmixture was conducted by filtration, the toluene was removed from theflitrate, and a molecular weight of the organoaluminum oxy-compound[B-2] obtained was measured in benzene by the cryoscopic method to findthat it was 610.

Polymerization

A thoroughly nitrogen-purged 2 liter stainless steel autoclave wascharged with 500 ml of toluene, and the system was then purged withpropylene gas. Successively, to the autoclave were added 1 mg atom eachin terms of Al atom of the organoaluminum oxy-compound [B-1] and theorganoaluminum oxy-compound [B-2] and 1.0×10⁻³ mmol of ethylenebis(indenyl)hafnium dichloride, and the temperature of the polymerizationsystem was elevated to 30° C. Thereafter, polymerization was carried outat 30° C. for 20 minutes while feeding propylene gas to tile totalpressure became 5 kg/cm² G to obtain 9.5 g of isotactlc polypropylenehaving [η] of 4.1 dl/g, Mw/Mn of 3.5, a melting point of 135° C., aboiling trichloroethylene-insoluble content of 0% by weight and aboiling n-pentane-soluble content of 0.2% by weight.

EXAMPLE 16

Example 12 was repeated except that the polymerization was carried outunder the total pressure of 7 kg/cm² G at 50° C. for 1 hours using 1 mgatom in terms of Al atom of (iso-C₄ H₉)₂ Al-O-Al(iso-C₄ H₉)₂ as theorganoaluminum oxy-compound [B-2] and 0.5 mg atom in terms of A1 atom ofthe organoaluminum oxy-compound [B-1] to obtain 35.1 g of isotacticpolypropylene having [η] of 2.2 dl/g, Mw/Mn of 2.1, a melting point of132° C., a boiling trichloroethyleneinsoluble content of 0% by weightand a boiling n-pentaneI soluble content of 0.3% by weight.

COMPARATIVE EXAMPLE 3

Example 16 was repeated except that the organoaluminum oxy-compound[B-2] was not used to obtain 2.4 g of isotactic polypropylene having [η]of 1.5 dl/g and a melting point of 5 130° C.

EXAMPLE 17

A thoroughly nitrogen-purged 1 liter glass autoclave was charged with328 ml of toluene and 22 ml of 1-octene, and the system was thenelevated in temperature to 70° C. while blowing ethylene gas thereinto.Successively, to the autoclave were added 0.4 mg atom in terms of Alatom of ##STR12## as the organoaluminum oxy-compound [B-2], 0.2 mg atomin terms of hl atom of the above-mentioned organoaluminum oxy-compound[B-1] and 3×10⁻³ mmol of ethylenebis (indenyl)hafnium dichloride toinitiate polymerization. The polymerization was carried out at 70° C.for 30 minutes while continuously feeding ethylene gas to thepolymerization system to obtain 12.3 g of an ethylene/1-octene copolymerhaving Mw/Mn of 2.49, MFR₂ of 7.2 g/10 min, MFR₁₀ /MFR₂ of 9.3 and adensity of 0.853 g/cm³.

What is claimed is:
 1. In a propylene random copolymer composed of structural units (a) derived from propylene and structural units (b) derived from α-olefin of 4 to 20 carbon atoms, the improvement which comprises that the propylene random copolymer has(i) the structural units (a) in an amount of 90 to 99 mol % and the structural units (b) in an amount of 1 to 10 mol %, (ii) an intrinsic viscosity (η) as measured in decahydronaphthalene at 135° C. of 0.5 to 6 dl/g, (iii) a melting point (Tm) as measured by a differential scanning calorimeter falling with in the range of

    90<Tm<155-3.5 (100-P)

wherein P is the propylene content (mol %) present in the copolymer, (iv) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) as measured by gel permeation chromatography of less than 3.5, and (v) a boiling trichloroethylene-insoluble content of less than 5% by weight.
 2. In a process for preparing propylene random copolymer, the improvement which comprises copolymerizing propylene and α-olefin or 4 to 20 carbon atoms at a temperature of 40° to 100° C. in the presence of a catalyst so that the resulting copolymer hasstructural units (a) derived from propylene in an amount of 90 to 99 mol % and structural units (b) derived from α-olefin in an amount of 1 to 10 mol %, a melting point (Tm) as measured by a differential scanning calorimeter falling within the range of

    9< Tm<155-3.5 (100-P)

wherein P is the propylene content (mol %) present in the copolymer, and a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) as measured by gel permeation chromatography of less than 3.5; wherein said catalyst is formed from (A) a halnium compound having a multidentate ligand in which at least two groups selected from the group consisting of cycloalkadienyl groups and substituted groups thereof are linked together via lower alkylene groups, and (B) an organoaluminum oxy-compound.
 3. In a propylene random copolymer composed of structural units (a) derived from propylene, structural units (b) derived from ethylene and structural units (c) derived from α-olefin of 4 to 20 carbon atoms, the improvement which comprises that the propylene random copolymer has(i) the structural units (a) in an amount of 90 to 99 mol % and the structural units (b) in an amount of 0.5 to 9.5 mol % and the structural units (c) in an amount of 0.5 to 9.5 mol %, (ii) an intrinsic viscosity (η) as measured in decahydronaphthalene at 135° C. of 0.5 to 6 dl/g, (iii) a melting point (Tm) as measured by a differential scanning calorimeter falling within the range of

    7< Tm<155-5.5 (100-P)

wherein P is the propylene content (mol %) present in the copolymer, (iv) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) as measured by gel permeation chromatography of less than 3.5, and (v) a boiling trichloroethylene-insoluble content of less than 5% by weight.
 4. In a process for preparing propylene random copolymer, the improvement which comprises copolymerizing propylene, ethylene and α-olefin of 4 to 20 carbon atoms in the presence of a catalyst so that the resulting copolymer hasstructural units (a) derived from propylene in an amount of 90 to 99 mol %, structural units (b) derived from ethylene in an amount of 0.5 to 9.5 mol % and structural units (c) derived from α-olefin in an amount of 0.5 to 9.5 mol %, a melting point (Tm) as measured by a differential scanning calorimeter falling within the range of

    7< Tm<155-5.5 (100-P)

wherein P is the propylene content (mol %) present in the copolymer, and a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) as measured by gel permeation chromatography of less than 3.5; wherein said catalyst is formed from (A) a hafnium compound having a multidentate ligand in which at least two groups selected from the group consisting of cycloalkadienyl groups and substituted groups thereof are linked together via lower alkylene groups, and (B) an organoaluminum oxy-compound.
 5. A heat sealing agent comprising the propylene random copolymer as claimed in claim 1 or
 3. 6. The propylene random copolymer of claim 1 wherein the structural units (a) are present in an amount of 92 to 98 mol % and the structural units (b) are present in an amount of 2 to 8 mol %.
 7. The propylene random copolymer of claim 6 wherein the α-olefin is 1-butene.
 8. The propylene random copolymer of claim 1 having an intrinsic viscosity (η) of 1 to 5 dl/g and a melting point (Tm) within the range of

    100<Tm<150-3.5 (100-P).


9. The propylene random copolymer of claim 1 having a molecular weight distribution of Mw/Mn of less than 2.5.
 10. The propylene random copolymer of claim 1 having a boiling trichloroethylene insoluble portion of less than 1% by weight and a boiling η-pentane soluble portion of less than 1% by weight.
 11. The propylene random copolymer of claim 3 wherein the amount of structural units (a), (b) and (c) is from 92 to 98 mol %, 1 to 9 mol % and 1 to 9 mol %, respectively.
 12. The propylene random copolymer of claim 11 wherein the α-olefin is 1-butene.
 13. The propylene random copolymer of claim 3 having an intrinsic viscosity (η) of 1 to 5 dl/g and a melting point (Tm) within the range of

    90<Tm<150-5.5 (100-P).


14. The propylene random copolymer of claim 3 having a molecular weight distribution (Mw/Mn) of less than 2.5.
 15. The propylene random copolymer of claim 3 having a boiling trichloroethylene insoluble portion of less than 1% by weight and a boiling η-pentane soluble portion of less than 2% by weight. 